docs: def _check_hash_view(self):
          """ Return infohash if view name refers to a single item, else None.
          """
          infohash = None
          if self.viewname.startswith('#'):
              infohash = self.viewname[1:]
          elif len(self.viewname) == 40:
              try:
                  int(self.viewname, 16)
              except (TypeError, ValueError):
                  pass
              else:
                  infohash = self.viewname
          return infohash